Last fall, a Mississippi bail bondsman and frequent YouTube vlogger noticed an alarming comment left on one of his videos. "I'm going to be a professional school shooter," said a user named Nikolas Cruz.

The YouTuber, 36-year-old Ben Bennight, alerted the FBI, emailing a screenshot of the comment and calling the bureau's Mississippi field office. He also flagged the comment to YouTube, which removed it from the video.

Agents with the bureau's Mississippi field office got back to him "immediately," Bennight said, and conducted an in-person interview the following day, on Sept. 25.

"They came to my office the next morning and asked me if I knew anything about the person," Bennight told BuzzFeed News. "I didn't. They took a copy of the screenshot and that was the last I heard from them."

FBI agents contacted Bennight again Wednesday, after a 19-year-old named Nikolas Cruz allegedly opened fire at Marjory Stoneman Douglas High School in South Florida, killing at least 17 people.

In an email on Sept. 24, Ben Bennight alerted the FBI to a "school shooting threat" made by a YouTube user named nikolas cruz.

In the wake of the deadly shooting, questions have emerged over whether officials and acquaintances had missed warning signs about the alleged shooter, a former student who was expelled from the high school last year for disciplinary reasons.

Classmates, relatives, and neighbors have described Cruz as a troubled "loner" who often talked about guns and flaunted his obsession with weapons on his social media accounts. And Jim Gard, a math teacher at the school, told the Miami Herald that the teen had previously been identified as a potential threat to other students.

Though his name matches the YouTube user flagged in September, FBI officials would not say whether they have confirmed that the account belonged to Cruz.

But around 4:30 p.m. on Wednesday — about 30 minutes after Cruz was taken into custody by police in Broward County — Special Agent Ryan Furr with the FBI's Miami field office called Bennight and left him a voicemail.

"I think we spoke with you in the past about a complaint that you made about someone making a comment on your YouTube channel," the agent said in the message, which Bennight provided to BuzzFeed News. "I just wanted to follow up with you on that and ask you a question with something that's come up, if you wouldn't mind giving me a ring."

A few hours later, Bennight said, FBI agents in Mississippi visited him again in person, pressing for more information about the YouTube user Nikolas Cruz.

"They asked me if I knew who he was. I didn't. I don't," Bennight said. "Then they left."

When contacted by BuzzFeed News, Furr declined to comment on the call and directed questions about the shooting to the FBI's public affairs office. The office did not respond to multiple calls or emails Wednesday night.

At a press conference Thursday morning, the FBI confirmed that it had received and looked into a tip about the "professional school shooter" comment on Bennight's YouTube channel, but could not uncover any details from the account.

"No other information was included in the comment, which would indicate a time, location, or true identity of the person who made the comment," special agent Robert Lasky told reporters. "The FBI conducted database reviews, checks, but was unable to further identify the person who made the comment."

The Nikolas Cruz YouTube account remained active until Wednesday evening. It has since been deleted, however, due to "multiple or severe violations of YouTube's policy on violence." YouTube did not immediately respond to BuzzFeed News' questions about the account.

"People leave pretty heinous comments on a pretty regular basis on this channel and I really didn't think anything of it," he told viewers. "But this comment said, 'I'm going to be a professional school shooter' and I knew I couldn't just ignore that."